1. Field of the Invention
The present invention relates to a door-holding control system for a vehicle slide door, which holds the slide door that is opened and closed by a drive source, e.g., a motor, while allowing the slide door to be moved from its standstill state by a required force.
2. Description of the Related Art
There is known a control system for automatically opening and closing, by use of a drive source, e.g., a motor, a slide door which is mounted on the side of a vehicle body while being slidable in the lengthwise direction. To drive the slide door for its opening/closing, suitable operation means is located near the driver sent or the door handle. The occupant intentionally operates the operation means.
To fixedly position the slide door when the vehicle in stopped, the control system inhibits the slide door from moving irrespective of the attitude of the vehicle being stopped by not releasing a clutch mechanism that is located between the drive source and the slide door.
In the conventional automatic door control system which includes a reduction gear and a clutch mechanism which are constituted such that a drive source, e.g., a motor, is impossible to turn in the reverse direction or requires a large force to turn in the reverse direction, that is, from the door side to the operation side, when the slide door is stopped and the clutch mechanism is declutched, the slide door is movable by manual operation. When the vehicle is stopped on a steeply sloped road, the mechanism fails to stop and hold the door. The door will be suddenly moved for its opening and closing.
When the sliding movement of the slide door is stopped and the clutch in left operated, the mechanism can hold the slide door even on the sloped road. To manually open and close the door thereafter, a large force is required, and therefore it is almost impossible to manually open and close the door. In some types of the automatic door control system, the start of the door movement made manually is detected and the drive source is driven to move the door. In this type of the door control system, it is undesirable that a force to operate the slide door is abruptly changed when the slider door starts to move.
A proposal is made in which when the slide door is stopped, a clutch voltage is gradually decreased to a voltage slightly higher than the clutch voltage when the slide door starts to move, whereby a power transmission maintenance force of the clutch mechanism is kept at such a value of force that the slide door is not moved by its weight but in movable by the manual operation.
When the slide door is manually operated during the control of the power transmission maintenance force, the clutch voltage increases to stop the slide door. If the manual operation is further continued, the clutch voltage is kept at a further increased value of voltage. The result is that the slide door cannot be opened and closed by manual operation.